Sand found underneath all the muck was used to line the four and a half miles of beach around the newly created Seven Seas Lagoon. Bay Lake and the 172-acre lagoon were then refilled with water from the surrounding wetland and stocked with more than 70,000 fish.

The Seven Seas Lagoon at Walt Disney World was not filled with a hose; it was created by excavating over 7 million cubic yards of earth and allowing the area to fill naturally. The process began in the late 1960s when engineers dug out the lagoon to create a "majestic gateway" for the Magic Kingdom. The earth removed during this excavation was used to raise the ground level of the Magic Kingdom by about 14 feet, allowing for the construction of the "Utilidors" (underground tunnels) beneath the park. Once the basin was dug, the lagoon filled through a combination of natural groundwater seepage and rainwater, which is abundant in Central Florida’s high water table. This created a 200-acre body of water with a depth of about 14 feet. Engineers also installed a sophisticated dam and lock system to connect the lagoon to the natural Bay Lake, ensuring the water levels remained stable. Today, the lagoon is home to several islands and serves as a functional and aesthetic centerpiece for the resort's ferry and monorail transport systems.